Automatic districting: what is “compacity”?
When carrying out the automatic districting of a territory, the main objective is often to get a “balanced” result, meaning a breakdown where the workload, number of clients, turnover, etc. are fairly distributed between sectors.
However, beyond this “balancing”, an automatic districting must also aim at creating sectors which, as far as possible, retain a coherence and geographic cohesion. Consequently, more “rounded” sectors, which do not extend too far from the origin point and can be visited homogeneously from the starting point, are often preferred.
- The sector circled in green is judged more “compact” than the light blue sector, since the municipalities composing it are distributed more evenly and it extends equidistantly to the East, West and North of its point of origin.
- The sector circled in red extends much too far North from its starting point. Consequently, it is judged less “compact” than its neighbor and will be less easy to visit.
The new automatic districting algorithms in C&D allow the user to take into account the notion of “compacity”: the compacity of each sector is measured through a compacity score to make sure it extends homogeneously in all directions around its starting point, while remaining as close as possible to that point.
Example of districting with a better compacity score: